Data from: Chimpanzee fathers bias their behaviour towards their offspring

Promiscuous mating was traditionally thought to curtail paternal investment owing to the potential costs of providing care to unrelated infants. However, mounting evidence suggests that males in some promiscuous species can recognize offspring. In primates, evidence for paternal care exists in promiscuous Cercopithecines, but less is known about these patterns in other taxa. Here, we examine two hypotheses for paternal associations with lactating mothers in eastern chimpanzees (Pan troglodytes schweinfurthii): paternal effort, whereby males associate and interact more with their own infants, and mating effort, whereby males invest in mothers and offspring for mating privileges. We found that fathers associated more with their offspring than they did with non-kin infants, particularly early in life when infanticide risk is highest. Additionally, fathers and their infant offspring interacted more than expected. Notably, association between fathers and mother–infant pairs did not predict the probability of siring the mother's next offspring. Our results support the paternal effort, but not the mating effort hypothesis in this species. Chimpanzees are one of the most salient models for the last common ancestor between Pan and Homo, thus our results suggest that a capacity for paternal care, possibly independent of long-term mother–father bonds, existed early in hominin evolution.

长期以来，学界普遍认为混交交配会削减父方投资——这是因为父方若照料非亲生幼崽，将承担潜在代价。然而，越来越多的研究证据表明，部分实行混交交配的物种中，雄性能够识别自己的后代。在灵长类动物中，混交的猕猴亚科（Cercopithecines）物种已被发现存在父方照料的证据，但其他类群中的此类模式仍鲜为人知。本研究针对东部黑猩猩（Pan troglodytes schweinfurthii）中父方与泌乳母方的关联模式，检验两种假说：其一为父方投资假说，即雄性会与自己的幼崽产生更多关联与互动；其二为交配投资假说，即雄性为获得交配权限而对母方及其后代进行投入。研究结果显示，父方与其幼崽的关联频次高于非亲缘幼崽，尤其在幼崽生命早期——此时杀婴风险最高。此外，父方与幼崽的互动频次也超出预期水平。值得注意的是，父方与母方-幼崽组合的关联程度，并无法预测该父方能否成功繁育母方的下一胎后代。本研究结果支持父方投资假说，而非该物种中的交配投资假说。黑猩猩是研究黑猩猩属（Pan）与人属（Homo）最近共同祖先的关键模型物种之一，因此本研究结果表明，父方照料能力或许早在人族演化早期就已出现，且该能力可能并不依赖于母方与父方的长期伴侣关系。